Instantaneous tension load release device



June 23, 1970 s. K. EDLESON 3,516,702

INSTANTANEOUS TENSION LOAD RELEASE DEVICE Filed June 26, 1968 LOCKING WEDGES WEDGE HALF-ANGLE 9 GREATER THAN THE COEFFICIENT OF FRICTION III! l'u llfllll l ullfl ..|||||||||l qfnmmniiiiil mul k' lllliawlhm TEETH CUT IN FINGERS BEAR ON WEDGES MOTION OF LINK HALVES 0N RELEASE STUART K. EDLESON INVENTOR ATTORNEY 3,516,702 INSTANTANEOUS TENSION LOAD RELEASE DEVICE Stuart K. Edleson, Dallas, Tex., assiguor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed June 26, 1968, Ser. No. 740,842 Int. Cl. B66c 1/00 US. Cl. 294-1 6 Claims ABSTRACT OF THE DISCLOSURE This is a device to instantaneously release a heavy tension load with essentially zero transition time between full and zero load. Tension members are interlocked by means of finger members and locking wedges, and by reason of the wedge angle design, when unrestrained the wedges start to accelerate out of the fingers to relieve the tension load.

This invention is related to and can be used with copending US. patent application Ser. No. 740,843 filed June 26, 1968, for Bowed Pellet Pack Warhead.

The present invention provides a minimum weight, minimum size device to instantaneously release a heavy tension load, with essentially zero transition time between full design load and zero load without the use of explosives. This non-explosive feature permits simplified storage, safe handling, and an absence of deleterious explosive effects on actuation. The device of this invention has the further advantage of avoiding undesirable bending effects when the restraint and release provisions are required to be asymmetrical and entirely to one side of the tension load line.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 shows an embodiment of the invention with the interdigitated fingers of tension members locked together with the locking wedges.

FIG. 2 shows the tension members separated upon release and ejection of the locking wedges.

FIG. 3 shows a plurality of tension members forming a loop.

FIG. 4 illustrates a rapid tension release device.

As can be seen from FIGS. 1 and 2, the load from each direction in tension members and 12 is routed to a set of interdigitated fingers. The tips 13 of the fingers 14 from the end of tension member 10 rests upon the base 15 of fingers 16 from the end of tension member 12, and tips 17 of fingers 16 rest upon base 18 of fingers 14. One side of fingers 14 and 16 are notched to form teeth to receive a pair of wedge-shaped shear bars 20, which lock the fingers together. The coefiicient of friction between the bearing surface of teeth of fingers 14 and 16 and the contacting sides of the wedges 20 is known within reasonable limits. The angle of the sides of wedges 20 is chosen to provide a small but positive ejecting force when the tension load is applied to tension members 10 United States Patent 0 3,516,702 Patented June 23, 1970 and 12. The ejecting force, F,;, on the wedges, in the locked condition, may be expressed as:

where T tension load 0=wedge half angle n =static coefficient of friction As can be seen, for a given angle 0, the coefiicient of friction could be sufliciently high that the numerator (sin 0- cos 0) would equal Zero or a negative value, ofi'ering no ejection force. The angle 0 therefore is chosen to provide a positive value of (sin 0p. cos 0) at the maximum expected value of u By then substituting the minimum expected value of ,u in the equation, the max imum expected ejection force can be determined. Any suitable external device may be utilized to restrain wedges 20 and then, when desired, rapidly release this maximum exepected ejecting force. Such an external suitable trigger device is shown in FIGS. 3 and 4, for example. The design of fingers 14 and 16 is such that the tooth angle, mating with the sides of wedges 20, undergoes essentially no angular deflection under the tension load on members 10 and 12.

Where zero transition time is desired, between restraint of full design load and zero load, tension members 10 and 12 must be initially loaded above the design load with an accompanying excess deflection in tension. Then, when the restraint force of the trigger device is suddenly removed, the wedges will start to accelerate out of the fingers. Due to the wedge angle, the fingers will start to pull apart as the wedges move outward, relieving this excess deflection. All of the excess deflection (and thus the excess load) is relieved just as wedges 20 clear the corners of the teeth notched in fingers 14 and 16. At this instant, the load drops from the residual, or design, load to zero over essentially zero time.

Wedge velocity, V, on clearing the fingers, may be expressed as:

i sin 9Mk cos 0 k tan 0 1/2 |:M (cos 0+,u sin 0) 2 where:

M=absolute mass of the wedges ,u =kinetic coefiicient of friction S= distance wedge moves from locked to full release k=spring constant-of each of the tension members, ex-

pressed as force required to stretch a unit length By choosing the variables to provide extremely high wedge velocity on clearing the fingers, the materials under essentially infinite load just prior to full release, will not have time to deform at the corners. When the wedge velocity is less than ideal, some tooth or wedge deformation will occur during release. To maintain zero transition time, this deformation is accounted for in the evaluation of the excess deflection required under the load supporting condition, prior to release.

A plurality of tension members with interdigitated fingers interlocked with wedges may be assembled in a loop, as illustrated in FIG. 3, for example, to restrain a bundle of rods or pellets, as in the aforementioned copending application for Bowed Pellet Pack Warhead.

The device shown in FIG. 4 is merely one minimumweight, minimum-size trigger device suitable to quickly release the wedges and thus the tension load. The Wedgerelease device is designed to restrain a tension load applied by two opposed lengths of looped, hard-drawn Wires 40 for example; wires were selected because they are capable of withstanding tension loads with a minimum of weight. This wedge-release device includes minimumweight end fittings 41 for these wires, to increase the ability of the wires to transmit the loss of tension impulse to a remote point in a minimum of time. This minimum-weight end fitting 41 also permits maximum utilization of the strain energy stored in tension wires 40 to remove the wires, on actuation, from interference with the load, i.e., the wedges 20, they have restrained.

This wedge-release device is capable of releasing a 300 pound tension load from full load to zero load in less than 150 microseconds.

As shown in FIG. 4, the tension load wires 40 are looped around two lightweight tubular end-fitting pins 41. Pins 41 are held in proximity to each other by the two halves 44 and 45 of a split, light, alloy link. The two halves of the split link are held together by a wire 46 which is wrapped around them under tension. Wrapping wire 46 is a fusible wire such as Pyrofuze, a material consisting of an aluminum core in a palladium sheath. When heated to 620 C. by passage of an electrical current therethrough, the two metals rapidly alloy together, the alloying being accompanied by the production of heat such that they appear to burn. Once initiated, this burning will continue along the length of the wire, until the wire is completely alloyed or is quenched by touching a heat sink.

By passing a current through the twisted ends of two lead fusible wires, said wires are ignited which in turn ignites the turns around the split link. Then tension load wires 40, acting on the end fittings 41, continuously provide forces tending to split apart the halves 44 and 45 of the link. When suflicient turns of the fusible coil 46 have burned through, the splitting forces break the remainder of the turns and the two halves 44 and 45 of the link accelerate rapidly in a direction normal to the tension load. This action very quickly relieves the tension constraint, permitting the two loops of tension wires 40 to spring apart (in the direction of the tension load) with a minimum of damping and remove any restraining force on wedges 20.

If desired, a small explosive link can be used in place of non-explosive link 44-45, or other suitable means for removing restraint on wedges 20.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A substantially instantaneous tension load release device, comprising:

(a) a pair of tension members having one end of each member connected together and having tension loads in opposite directions,

(b) the connecting ends of said pair of tension members having interdigitating finger means,

(c) wedge locking means,

(d) said finger means being notched to form teeth to receive said locking means for locking said finger means together when interdigitated,

(e) the sides of said locking means being at an angle chosen to provide a positive ejecting force when said tension members are under a chosen tension load,

(f) rapid release means for restraining said locking means from ejecting from the notches in said finger means un il desire (g) said rapid release means for restraining said Wedge locking means comprising:

(1) two opposed lengths of looped wires,

(2) each of said opposed lengths of looped wires being looped around an end-fitting pin,

(3) a link means for holding said end fitting means and thus said opposed lengths of looped wires together,

(4) said link means being split lengthwise along the direction of said lengths of looped wires and consisting of two link halves,

(5) means for retaining the two halves of said split link means together,

(6) said means for retaining the two halves of said split link means together being operable on signal to very quickly separate the two halves of said split link releasing said looped wires and removing any restraining forces on said Wedge locking means.

2. A tension load release device as in claim 1 wherein said wedge locking means ejecting force, F is defined by the equation:

where T is the tension load, 0 is the wedge half angle, and a is the static coeflicient of friction between the bearing surfaces of the notches in said finger means and the contacting sides of said wedge locking means.

3. A tension load release means as in claim 1 wherein the tips of said finger means of each said tension member rest on the base of the finger means of the other tension member.

4. A substantially instantaneous tension load release device, comprising:

(a) a pair of tension members having one end of each member connected together and having tension loads in opposite directions,

(b) the connecting ends of said pair of tension members having interdigitating finger means,

(c) wedge locking means,

(d) said finger means being notched to form teeth to receive said locking means for locking said finger means together when interdigitated,

(e) the sides of said locking means being at an angle chosen to provide a positive ejecting force when said tension members are under a chosen tension load,

(f) rapid release means for restraining said locking means from ejecting from the notches in said finger means until desired,

(g) said rapid release means for restraining said wedge locking means comprising:

(1) two opposed lengths of looped wires,

(2) each of said opposed lengths of looped wires being looped around an end-fitting pin,

(3) a link means for holding said end-fitting pins together,

(4) said link means being split lengthwise along the direction of said lengths of looped wires and consisting of two link halves,

(5) fusible means for retaining the two halves of said split link means together,

(6) tension on said looped wires providing forces tending to split apart the halves of said split link (7) said fusible means being ignited and burned through on passing an electrical current therethrough allowing the two halves of said split link to separate and accelerate rapidly in directions normal to the tension load on said looped wires thereby very quickly releasing said looped wires and removing any restraining forces on said wedge locking means.

5. A tension load release device as in claim 4 wherein said wedge locking means ejecting force, F is defined by the equation:

sin 0 cos 0 F2 2T [cos 0+1 sin 0] where T is the tension load, 0 is the wedge half angle, and ,u is the static coeflicient of friction between the bearing surfaces of the notches in said finger means and the contacting sides of said wedge locking means.

6. A tension load release means as in claim 4 Wherein the tips of said finger means of each said tension member rest on the base of the finger means of the other tension member.

References Cited UNITED STATES PATENTS 2,786,392 3/1957 Niedling.

2,826,119 3/ 1958 Barrowman 89-1.5 3,088,768 5/1963 Willison 294-83 X 3,093,031 6/1963 Damm 891.5

SAMUEL W. ENGLE, Primary Examiner U.S. Cl. X.R. 

